Adjustable stop crimper



May 29, 1956 l. v. HlTT ADJUSTABLE STOP CRIMPER Filed July 25, 1952 IraBY 7% 31 ATTORNEY United States Patent O ADJUSTABLE STOP CRIMPER IraVirgil Hitt, Waynesboro, Va., assignor to E. L du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware Application July25, 1952, Serial No. 300,871

4 Claims. (Cl. 19-'"66) This invention relates I to an improved stutterbox crimper for more uniformly crimping bundles or tows of filaments.More particularly this invention relates to means for controlling theuniformity and intensity of crimp imparted to a bundle of'continuousfilaments to be out into staple for subsequently processing into spunyarn.

Inadequate and non-uniform crimp applied to bundles of continuousfilaments of polyacrylonitrile or similar polymers subsequently cut intostaple has been the cause of troublesome processing of the staple andnon-uniform and low quality spun yarn therefrom. Variations in crimp andcrimp intensity were often the cause of too great or too little masscohesion or the cause of lap splittin-g, and in some cases a staplestock could not be processed at all satisfactorily. A thorough study ofthe many factors affecting satisfactory staple processing brought outthe necessity for uniform and adequate crimp. The frequeney anduniformity of crimp is affected in many Ways and although highlysatisfactory results were secured at times, reproductibility was mostuncertain prior to this invention.

An object of this invention is to provide an improved means for crimpingbundles of continuous filaments. Another object of this invention is toprovide a means for controlling the action of the crimper to impart tothe filaments passing thereinto a uniform crimp of the desired crimpintensity over long periods of time. Other objects will be apparent fromthe description that follows.

In the figures:

Figure 1 is a diagrammatic sketch of the apparatus and Figure 2 is takenon line 2-2 of Figure l to illustrate the nature of the crimp.

The objects of this invention are accomplished by modifying the crimper,as is described hereinafter. Briefly the improvement resides in limitingthe movement of the pivotal feed roll so that it cannot contact thefixed roller and maintaining under all circumstances a clearance of atleast a few thousandths of an inch therebetween. As shown in Figure lthe adjustable stop comprises a shoe I mounted on an adjustable screw 2through a fixed bar 3.

Earlier experiments had established the possibility of two types ofcrimp that could be formed in the tow depending on the preciseconditions of operation. One type, which will be referred to as Type Afor convenience, is desirable, being uniform and of the right frequencyand intensity. This crimp is characterized by a herringbone appearancein the crimped tow in the box and as it comes from the box, and thecrimp lies in a plane parallel to the faces of the crimper feed rolls,as is shown in Figure 2 and represented by reference number 4. On theother hand, a crimp may be obtained which takes place in a plane atright angles to that of Type A crimp; that is, the crimp is in a planeperpendicular to the faces of the crimper feed rolls. This crimp isundesirable in that it is random in its formation and is, therefore,difiicult to control and characterize. Hereinafter this crimp will becalled type B crimp. One of the major requirements to produce crimp ofthe A type is relatively low pressure at 2,747,233 Patented May 29, 19562 the nip of the crimper feed rolls, whereas greater pressure betweenthese rolls brings about crimp of the B type.

Normally a tow 5 of continuous filaments of 70,000 to 300,000 or moretotal denier is finished, steamed, and fed into a crimper such as thatdescribed in my U. S. Patent 2,311,174. With the tow of filaments fedunder substantially optimum conditions as to speed, finishconcentration, temperature, etc., the desired type A crimp may besecured, although a relatively slight increase in pressure on the towpassing between the feed rolls 6 and 7 will bring about production oftype B crimp. For instance, with a pressure cylinder and pistoncombination (not shown) or a spring device 8 provided to exert apressure of 10 pounds downward against the end of the pivot arm 9,thereby urging the movable roll 6 toward the fixed feed roll 7, type Acrimp of the desired uniformity and intensity resulted; with a 50%pressure increase the crimp completely changed to type B. With theoriginal pressure decreased by 50%, the feed rolls continually wrappedback and made operation impossible. Due to frictional changes with time,especially between the sides of the feed rollers and the insert members10 and 11 (shown in Figure 2), it was unusual for the actual .pressureexerted at the nip of the rolls to vary widely without the primary forceacting to urge the rolls together being changed in any way. In fact, thehigh frictional resistance to change in position of the movable rollcaused an exaggerated movement of the roll when a movement occurred,resulting in bouncing and wide fluctuations in pressures. As a result,the tow of filaments passing through the crimper became crimpe'd in ahaphazard manner being partly type A and partly type B crimp with thecrimps varying widely in frequency and intensity. Such production, whenout into staple for processing and converting into spun yarn, led to thenumerous dilii'culties previously mentioned.

The provision of the limiting stop of this invention essentiallyeliminates variation in pressure at the nip of the rolls. The clearanceadjustment will, of course, depend on the size of the tow being fedtherethrough and the width of the crimper rolls. For an 85,000 deniertow of acrylonitrile polymer filaments of about 3 denier per filament insize fed between crimper rolls 1 inch in width, the stop should beadjusted for a minimum clearance of from 0.012 inch to 0.018 inch andpreferably about 0.015 inch. With a smaller tow or wider feed rolls, theclearance should be reduced and vice-versa for a larger tow or narrowerrolls, or both. Usually, however, this minimum clearance should be noless than 0.005 inch, nor more than 0.05 inch. Furthermore, with thelimiting stop installed, the force imposed to urge the rolls togethermay be adjusted to a considerably higher value than that which must beused to produce the desirable type A crimp without the stop. The use ofthe greater pressures positively eliminates the sensitivity of the feedroll pressure and nonuniform crimp. Moreover, by operating with a higherforce more rapid recovery of proper roll clearance is obtained after thepassage of some extra thick portion of tow. This minimizes the tendencyfor the tow to wrap back on previous rolls because of a sudden loss ofgrip by the crimper rolls.

Example An 85,000 denier tow of about 3 denier acrylonitrile polymerfilaments was prepared by evaporative spinning of acrylonitrile polymerdissolved in dimethylformamide, washing the filaments substantially freeof solvent, drawing 4X and combining a number of strands. This tow wasthen led over a finish roll, through a steam cell, and over, under andbetween pin guides to shape the tow into a uniform bundle of properwidth before introducing it into the bite of the feed rolls of thecrimper. The crimper was preheated by the introduction of low pressuresteam and a temperature of about 150 F. was maintained in the tow whileit was being crimped. The crimper feed rolls, 1 inch in width, wereadjusted to a minimum clearance of 0.015 inch by means of the stopdevice of this invention and the pressure cylinder was adjusted toimpart a load of 15 pounds against the end of the pivot arm to hold themovable feed roll up against the stop. The tow was introduced into thecrimper at the rate of 132 y. p. m. and emerged against the action ofthe weighted clapper plate 12 uniformly crimped with about 10 crimps perinch. After cutting this tow into 1%, 2, 2 /2 or 4 inch staple, it wasfurther processed and spun without difficulty into uniform high strengthyarn.

The use of the stop of this invention materially reduces the pressureapplied on the tow in the nip of the crimper feed rolls and allows thecrimp to form in a plane parallel to the faces of these rolls. Yet,there is suflicient squeezing action to feed the tow properly along intothe crimper against the back pressure caused by the weighted clapperplate. If a heavy section of tow comes along, the rolls spread apart asbefore but because a greater force tending to close the rolls is beingapplied, the separation of the rolls is less frequent. As a consequence,repeated bouncing and oscillating of the pivot roller 6 is substantiallyeliminated and importantly the rebound from the more widely openedposition is stopped short of pounding and compressing the tow so thatthe desirable A type crimp is not lost.

The apparatus of this invention permits the assured Any departure fromthe above description which conforms to the present invention isintended to be included within the scope of the claims.

I claim:

1. In a crimper having cooperating feed rolls one of which is mounted ona pivot member so as to be capable of being moved away from the otherroll, the improvement comprising a stop limiting the movement of saidpivotal feed roll so that it cannot come in contact with said otherroll.

2. In a crimper having cooperating feed rolls one of which is mounted ona pivot member so as to be capable of being moved away from the otherroll, the improvement comprising a stop for maintaining a minimum gapbetween said feed rolls.

3. In a crimper having cooperating feed rolls one of which is mounted ona pivot member to form a nip with the other feed roll, the improvementcomprising an adjustable stop comprising a shoe mounted on an adjustablescrew and located on said pivot member to maintain a minimum clearanceof at least a few thousandths of an inch between said feed rolls.

4. Apparatus in accordance with claim 3 wherein said clearance isbetween about 0.005 to about 0.05 inch.

References Cited in the file of this patent UNITED STATES PATENTS2,044,135 Taylor June 16, 1936 2,090,669 Dreyfus Aug. 24, 1937 2,245,874Robinson June 17, 1941 2,311,174 Hitt Feb. 16, 1943 2,698,970 WickerJan. 11, 1955 FOREIGN PATENTS 487,711 Great Britain June 24, 1938

1. IN A CRIMPER HAVING COOPERATING FEED ROLLS ONE OF WHICH IS MOUNTED ONA PIVOT MEMBER SO AS TO BE CAPABLE OF BEING MOVED AWAY FROM THE OTHERROLL, THE IMPROVEMENT COMPRISING A STOP LIMITING THE MOVEMENT OF SAID